Bug 983605 - Allow to administrator to change the default 'rhc ssh' motd

This patch will allow to administrator change the default `rhc ssh APP` welcome message from the default 'Online' message to a custom one via the `MOTD_FILE` option in node.conf.

By default the Online message will be used. Also, since on Online AFAIK the /etc/motd has the same content, the default message could be removed from the `rhcsh` entirely and the default value for MOTD_FILE could be '/etc/motd'.. Thoughts?